Design

Chief Engineer Jiro Horikoshi designed the Mitsubishi A6M as a replacement for the A5M. The A5M outperformed all of its rivals in China leading to the belief that a highly maneuverable fighter was better.

A 12-Shi requirement for a new fighter was issued on January 17, 1938, to Nakajima and Mitsubishi. Convinced it was impossible to meet the requirements, Nakajima withdrew. The requirements were for a fighter:

300 mph at 13,000', 311 mph at 13,125' / 4,000 m

climb to 9,840' / 10,000' / 3,000 m in 9 minutes 30 seconds

wingspan of no more than 12 m in length to fit the elevators on the Imperial Japanese Navy's carriers

take off within 230' / 70 m with a 40' per second / 27 knots head wind

armament of two 7.7 mm machine guns and two 20 mm cannons

carry two 132 lb / 60 kg bombs

Mitsubishi was developing the 11-Shi bomber at the time and didn't want to divert resources to a new fighter that it too thought was impossible to build. In exchange for letting Mitsubishi drop the 11-Shi project, the Imperial Japanese Navy talked Mitsubishi into developing the "impossible" fighter.

Once testing was complete the Imperial Japanese Navy gave it its designation, the A6M1 Rei Shiki Sento Ki (Type 0 Carrier borne Fighter).

The Zeke name came from the Japanese year 2600 that it was designated.

Engines

The first two prototypes had the Mitsubishi Zuisei 13 (875 HP) engine installed. On the third prototype carried the Nakajima Sakae 12 (950 HP) engine. The Sakae 12 was selected and it resulted in the need for making the A6M even lighter so armor plate and self sealing fuel tanks were not included in the initial design.

The engines were very good, but as the war progressed quality declined.

Undercarriage

The undercarriage of the A6M was wide and sturdy.

Fuel Tanks

One of the main weaknesses of the A6M Zero was that it didn't have self sealing fuel tanks.

There were three fuel tanks, one in front of the pilot and one in each wing root.

Cockpit

Another weakness of the A6M Zero is that the pilot had no armor until very late models.

Fuselage

In the rear of the fuselage was a canvas floatation bag in the case of a ditching at sea.

The center section was made an integral part of the wing which save weight and aided in maintenance. The front and rear sections of the fuselage were removable.

Wings

To make the A6M as light as possible the wing was developed to be in one piece and made from lightweight Extra-Super Duralumin.

Main Armament

The prototype had two 7.7 mm Type 97 machine guns that were in the top of the fuselage with cocking mechanisms coming out the instrument panel.

Two 20 mm Oerlikon cannons (license built by Dai-Nihon Heiki Company as Type 99s) were in the wings. These were outside the landing gear.

A6M2

Engine

The Sakae 12 engine resulted in the the carburetor intake being made integral in the cowling and placed in the lower part of it.

Cockpit

At the rear the glass panels were shortened.

Wings

The A6M2 Model 11s were tested on the Soryu in June 1940. It exceeded all expectations but it was found that the wing tips could sustain damage while being moved on the elevators. The Model 21 was designed with 20" on each end of the wing being able to fold upwards to make for more room on the elevators.

A6M2-K, A6M5-K

Originally some A6M2s in the field were converted in 1942 to two seaters to be used for reconnaissance and command duties.

Specifications for a dedicated trainer was given in 1943. Dai-Nijuichi Kaigun Kokoshu (21st Naval Air Depot) designed the A6M2-K.

The instructor was behind the student. The trainer's seat was where the radio and other equipment was located. The student's part of the cockpit was permanently open.

Dual controls were installed. The fixed tail wheel was larger than the A6M fighters. Wheel covers and the wing cannons were removed to save weight.

A stability fin was added just in front of the horizontal stabilizer.

A6M3

Later models of the A6M3 had the folding wingtips not installed.

Engine

Nakajima produced the Sakae engine which had a two stage supercharger. The engine was longer and required the firewall to the rear by 8" / 20 cm. This caused the fuel tank to have to be reduced in size.

The larger engine resulted in changing the cowling to be more rounded and larger. Propeller was slightly larger.

Wings

The first two A6M3s produced had the folding wingtips but they were removed in the hopes to increase speed. This was to compensate for the heavier engine. It was hoped that the shorter wings would make the A6M3 more maneuverable, but this didn't happen.

Allied Naming

In honor of Air Force General "Hap" Arnold the A6M3 Model 32 was called the "Hap." However, he did not appreciate the gesture and ordered the designation to be changed to "Hamp." After captured examples of the Model 32 were captured the name was revised to Zeke 32.

A6M5

The A6M5 was to be a temporary expedient until the replacement carrier based fighter, Mitsubishi A7M Reppu, was developed. As the A7M failed the A6M5 ended up being the most produced of the A6M series.

It was to be simplified for production and increase the diving speed. A heavier gauge metal was used in the wings. Diving speed was increased to 410 mph.

A6M6, A6M7, A6M8

Mitsubishi tried to improve the capabilities of the A6Ms with the A6M6, A6M7, and A6M8. But due to United States bombing campaign it was very difficult on industry.

Speed and Range Comparison

Prototype

On March 23, 1939, the first prototype had to be disassembled at the Mitsubishi plant, and transported to the Kagamigahara naval air base on two oxcarts.

The A6M1 prototype first flew on April 1, 1939 at Kagamigahara with Katsuzo Shima at the controls. It had a Mitsubishi Zuisei 13 (780 HP) radial engine installed. He rolled it down the runway and lifted off a few feet off the ground before settling back onto the runway.

During the testing it was found that there was a vibration in the engine that couldn't be explained. Hirokoshi had the two blade propeller replaced by a constant speed three blade propeller. The 12-Shi was the first Japanese plane to have a constant speed propeller. This was tested on April 17, 1939, and the vibration in the engine was nearly eliminated. This prototype was taken on 119 flights for a total of 43 hours and 26 minutes of air time.

Second Prototype

The second prototype was delivered on October 25, 1939. It had better elevator controls. It went to the Navy's test center at Yokosuka Air Base. Armament trials began a short time afterwards.

On March 11, 1940, the plane had an explosion in flight and unfortunately killed the test pilot.

Third Prototype

The third prototype (designated the A6M2) was fitted with the Nakajima NK1C Sakae 12 engine. It flew on December 28, 1939 / January 18, 1940 for the first time.

Accepted for Service

On July 31, 1940, the A6M was accepted for service with the Navy.

A6M5

The prototype A6M5 (the 904th A6M3 converted) first flew in August 1943.
The A6M5 Model 52 prototype first flew in the summer of 1943.

A6M6

The A6M6 Model 53c prototype first flew in November 1944. Due to engine failures the A6M6 was abandoned.

A6M7

The A6M7 Model 63 prototype first flew in May 1945.

A6M8

The A6M8 Model 54c first flew in April 1945.

Production

The Zero was the most produced Japanese fighter.

The A6M2 first flew on December 28, 1939.

The first A6M2-K was completed in November 1943.

The A6M3 was first flown in June 1941. Production ended in the middle of 1943.

China Debut

On July 21, 1940, fifteen preproduction models were sent to the 12th Rengo Kokutai (air corps) at Hankow. Lt. Tamotsu Yokoyama led the first A6Ms into combat escorting 54 G3M2 Nells to Chungking.

First Battle

During the fourth mission on September 13, 1940, Chinese Air Force I-15s and I-16s intercepted the returning formation. During the battle all 27 Chinese fighters were shot down without a loss to the Japanese.

From September 1940 to September 1941 A6Ms shot down 99 Chinese aircraft with only a loss of two A6Ms to ground fire. In September 1941 they were re-deployed to prepare for the attacks on the Allies.

Pearl Harbor

At Pearl Harbor there were 125 A6M2s used, and nine failed to return.

The Japanese Navy had 521 A6Ms with 328 of them being A6M2s.

Midway Pinnacle

The A6Ms were the best fighter in the Pacific through the Battle of Midway. After that the A6Ms were being quickly outperformed by P-38 Lightnings and F6F Hellcats.

A6M2

The Model 11 saw its first combat in China and the first kills were in September 1940 when 13 A6M2s fought 27 Chinese Polikarpovs and shot all of them down.

Units

In central China the 12th Kokutai had around 30 Model 11s. In southern China the 14th Kokutai had around 9.

Burma, Malaya, Pearl Harbor and the Philippine Islands

The A6M2 was the primary version that was used in the first months of the war in the Pacific. It made up 2/3 of the Japanese Navy's fighter force.

First Complete Airframe

In July 1942 the Americans were able to retrieve a complete A6M2 airframe from the Aleutian Islands, where it had been forced to land. A report was issued on September 4, 1942, after tests were conducted.

A6M2-K, A6M5-K

The A6M2-K first entered service in early 1944.

Some ended up being used as Kamikaze planes.

A6M3

The A6M3 entered service in 1942. Pilots weren't as happy with the A6M3 as with other A6M models as it was only slightly faster than the A6M2.

Many of the A6M3 Model 32 were used for training in Japan.

First Unit

The 2nd Kokutai was the first to receive the A6M3 Model 32 in the spring of 1942. The 2nd Kokutai was located in New Guinea and due to the A6M3s shorter range these fighters were unable to take part in the battles over Guadalcanal.

Guadalcanal

The A6M3 Model 22 appeared over Guadalcanal in August 1942.

Zuikaku

Some A6M3 Model 22s served on the Zuikaku.

A6M5

The A6M5 entered service in October 1943.

It's best speed for combat was 180 mph or less.

Kamikaze

On October 25, 1944, the Shikishima kamikaze sent five A6M5s to attack the St. Lo and sank it.